DESCRIPTION: Development of the Drosophila embryo is characterized by a wide variety of cellular movements and cell shape changes. This research examines at the molecular level the role of conventional nonmuscle myosin (myosin II) in cell shape changes during development. The investigator has previously shown that myosin II plays an essential role in cytokinesis, cell sheet morphogenesis, and cell locomotion. The basic goals of this renewal application is to continue the studies of myosin II but to focus on how regulation of myosin function sculptures the embryo. Three specific aims are described. First, myosin regulation will be investigated through a genetic analysis of myosin light chain function and by a directed analysis of myosin heavy chain phosphorylation. Second, myosin-associated proteins that have a possible role in regulating myosin function will be identified by biochemical and genetic methods. Third, a continuation of investigations into the role of myosin during embryogenesis. Findings from this project will define cellular elements that regulate myosin function and identify the supramolecular structures that transmit myosin-generated forces to the cortex and cytoplasm during the complex cellular rearrangements in the Drosophila embryo. This basic level of research is relevant to the understanding of how abnormal cell movements during embryonic development or later in the adult contribute to birth defects and cancer.